如何在if語句中檢查NSNotification

Question

我正在嘗試運行以下代碼，除非發送了NSNotification 。 我不知道如何將NSNotification放在if語句中：

if (!self.subViewControllerProv) {
    self.subViewControllerProv = [[ProvViewController alloc] init];
}


[[NSNotificationCenter defaultCenter] addObserver:self
    selector:@selector(handleNotification:) name:@"SomeNotification" object:nil];

到概括：如果NSNotification觀察消息。然后alloc和init的ProvViewController如果不是那么沒有。

Answer 1

嘗試添加一個帶有標志的實例變量，該標志用於通知是否已觸發，在-handleNotification：中設置該標志，然后檢查是否合適。

- (void)handleNotification:(NSNotification*)notification {
    _notificationWasPosted = YES;
}

...

if (!_notificationWasPosted && !self.subViewControllerProv) {
    self.subViewControllerProv = [[ProvViewController alloc] init];
}

Answer 2

那么做這樣的事情呢：

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleNotification) name:@"SomeNotification" object:nil];

接着

-(void) handleNotification {
    //BOOL _hasBeenSent in your interface
    _hasBeenSent = YES;
}

然后在你的代碼中

if(_hasBeenSent) {
    NSLog(@"The notification has been sent!");
}